Leading multiple lives in 'Complete Unknown' (R)

“Complete Unknown” opens with a dazzling series of brief, interconnected flashbacks, quick glimpses of a series of radically different women. But are they so different after all?

Boom, boom, boom, we get brief hits of Connie, a traveler renting a room; Kate, a take-charge emergency room nurse; Mae, a magician’s assistant in China. Another woman watching a house in Ohio, yet another in a relationship in Britain.

Disorienting, yes, but something unites them: Against all reason, they’re all the same person, all played by Rachel Weisz in the opening salvo of “Complete Unknown,” an intriguing entertainment that’s invigorated by smart filmmaking and potent acting by the virtuosic Weisz and her fine co-star, Michael Shannon.

When “Complete Unknown” kicks in, Weisz’s character is presenting herself as a biologist named Alice Manning involved in a Long Island examination of the first new species of frog discovered in North America in 27 years.

But while that may be true for now, the reality, as that opening montage indicated, is that this woman is a facile shapeshifter, capable of making herself up as she goes along and willing to discard her lives like second skins when they no longer suit her.

Directed by Joshua Marston (best known for “Maria Full of Grace” and co-writer of the script with Julian Sheppard), “Complete Unknown” does more than divert in a slyly implausible way.

The film, whose title references the Bob Dylan song “Like a Rolling Stone,” also raises provocative questions about what is real in life and what is not, about whether embracing radical change creates a sense of possibility or amounts to betrayal, to running away.

None of this would be possible, of course, without Weisz, one of the most effective actresses working today, and her intoxicating movie-star performance.

Weisz’s ability to convincingly be all these people is of course impressive, but that’s kind of a given. More to the point is the way she portrays the individual underneath it all, sharing both the high-wire rush of a big-lie life and how fraught that entire dynamic must be. While there’s a certain amount of contrivance in this situation, Weisz’s acting enables you to forget all about it.

“Complete Unknown’s” other key player is Tom, artfully played by Shannon, a serious guy who works at a nonprofit think tank concerned with agricultural policy. If Shannon plays a character, it’s a given he’s going to be intense about his work, and Tom very much is.

Tom’s wife, Ramina (Azita Ghanizada), a gifted jewelry designer, is passionate about her work as well, but that is about to lead to a problem. Ramina’s been accepted at an elite two-year design program in San Diego, but Tom is so wrapped up in his work he’s not sure if he can leave their Brooklyn brownstone and relocate to the West Coast as he said he would.

Tom’s closest colleague at work is Clyde (the versatile Michael Chernus), a nerdy policy wonk. He thinks he’s being smooth when he chats up Alice at the cafeteria in his building, but in fact Alice, not surprisingly, is the one in charge, deftly reeling Clyde in like a trout.

So when Tom has a birthday dinner party and of course invites Clyde, he brings Alice along, and that’s when things start to get interesting.

Because as soon as Tom sees Alice, he can’t shake the feeling that he’s seen her before, knows her from somewhere, a feeling that gets only stronger the more convincingly Alice denies any previous acquaintance.

Gradually, “Complete Unknown” manages things so that Tom and Alice can spend time alone, and the film deftly turns, even given the presence of top supporting actors such as Kathy Bates and Danny Glover, into an increasingly intimate two-hander.

Slowly but inevitably, these characters reveal themselves to each other and to us.

Their skill and the careful way Marston unfolds their story turns what could have been merely a device into something that is considerably more.